Update docstrings for FileWatcher class and add unit test coverage

[NeonDaniel]

No description provided.

[codecov]

Codecov Report

Merging #152 (659a50c) into dev (57f7909) will increase coverage by 10.72%.
The diff coverage is 25.70%.

@@            Coverage Diff             @@
##             dev     #152       +/-   ##
==========================================
+ Coverage   0.00%   10.72%   +10.72%     
==========================================
  Files         47       78       +31     
  Lines       5482     7086     +1604     
==========================================
+ Hits           0      760      +760     
- Misses      5482     6326      +844     

Impacted Files	Coverage Δ
ovos_utils/__init__.py	0.00% <0.00%> (ø)
ovos_utils/bracket_expansion.py	0.00% <0.00%> (ø)
ovos_utils/configuration.py	0.00% <0.00%> (ø)
ovos_utils/device_input.py	0.00% <0.00%> (ø)
ovos_utils/dialog.py	0.00% <0.00%> (ø)
ovos_utils/enclosure/__init__.py	0.00% <0.00%> (ø)
ovos_utils/enclosure/api.py	0.00% <0.00%> (ø)
ovos_utils/events.py	0.00% <0.00%> (ø)
ovos_utils/file_utils.py	0.00% <0.00%> (ø)
ovos_utils/fingerprinting.py	0.00% <0.00%> (ø)
... and 56 more